1. Field of the Invention
The present invention relates to a cell packing material and a method of manufacturing the same, and more particularly, to a cell packing material including an outer layer having improved physical properties, which is capable of being easily molded into a pouch and exhibiting excellent durability, and the like, and a method of manufacturing the same.
2. Discussion of Related Art
In general, cells such as secondary batteries are packed in flexible pouches. This is particularly true of polymer batteries such as lithium polymer batteries or secondary battery cells such as electrical double-layer capacitors or pseudo-capacitors. Cell pouches for packing such cells have been formed of a multilayer packing material (in the form of a sheet or film) in consideration of gas barrier properties, electrolyte resistance, and thermal adhesivity.
FIG. 1 is a cross-sectional view showing a cell packing material according to the prior art.
Referring to FIG. 1, the cell packing material is in the form of a sheet (or film). In this case, the cell packing material generally has a laminated structure including a sealant layer 1, a gas barrier layer 2 formed on the sealant layer 1, and an outer layer 3 formed on the gas barrier layer 2.
For example, Korean Patent Nos. 10-0574819, 10-0887616 and 10-1050007, and Korean Unexamined Patent Application Publication No. 10-2001-0052645 disclose cell packing materials (cell pouches) each having the laminated structure as described above.
The cell pouches are prepared by processing a packing material on a film (or a sheet) having the above-described laminated structure in the form of a pocket or a box. Cell components such as an anode, a cathode and a separator are packed in such a cell pouch in a state in which the cell components are dipped in an electrolyte solution.
The sealant layer 1 comes in contact with an article disposed in the innermost layer to be packed, that is, a battery cell. In this case, after the cell components are packed in the cell pouch, the entrance of the cell pouch remains hermetic since the sealant layers 1 adjoin each other to thermally adhere (thermally seal) the entrance of the cell pouch. For this purpose, a thermally adhesive resin is used as the sealant layer 1. The gas barrier layer 2 serves to prevent the flow of a gas into and from the cell pouch. In this case, an aluminum (Al) thin film (i.e., Al foil) is widely used as the gas barrier layer 2.
Also, the outer layer 3 serves to protect the gas barrier layer 2. In this case, the outer layer 3 should be chosen in consideration of heat resistance or wear resistance. For this purpose, polyethylene terephthalate (PET) is widely used as the outer layer 3.
However, the cell packing material according to the prior art has a problem in that moldability may be degraded when the cell packing material is processed into pouches. More particularly, the cell packing material is bent in the form of a pocket or box to be processed into a pouch as described above so as to pack the cells. In this case, the PET constituting the outer layer 3 has poor bending processability due to its low elongation. Therefore, PET has a problem in that it is difficult to mold into a pouch.
Further, the PET constituting the outer layer 3 has problems in that it has poor wear resistance, scratch resistance and chemical resistance and exhibits degraded durability. In particular, the surface of the PET may be easily scratched, and the scratches are not easily erased. Therefore, in the preparation of the cell packing material, in most cases, a nylon resin layer and a PET layer are sequentially laminated on the gas barrier layer 2 so as to reinforce durability, and the like. In this case, the cell packing material has problems in that it has poor wear resistance and scratch resistance as well as poor moldability, and it is also manufactured through complicated processes.